1. Field of the Invention
The present invention relates to an ink jet recording head adoptable for use in wide industrial fields, which is not only applicable to an office use printer, but also, to a printer capable of printing on cloths, coloring base plate for color filter use, and some other recording medium. The invention also relates to a method for manufacturing such ink jet recording head. More particularly, the invention relates to an ink jet recording head for which an elongation is designed for the discharge energy generating element substrate, as well as to a method for manufacturing such ink jet recording head.
2. Related Background Art
The structure of the conventional ink jet recording head itself for which an elongation is designed is substantially the same as the structure of the conventional ink jet recording head which is formed comparatively short. As shown in FIG. 8, on a base plate 106, a heater board 204 is installed with discharge energy generating elements (not shown) such as electrothermal converting devices or the like, and on it, is further installed a ceiling plate 205 formed by silicon, resin, or the like which is provided with fine groove patterns thereon. The heater board 204 and the ceiling plate 205 are bonded or held down by use of a spring unit after a process of ceiling plate bonding. As shown in FIG. 9, the ceiling plate 205 is provided with an SUS rod which penetrates it in the longitudinal direction in order to secure the straightness thereof.
The ink, which is supplied through a filter (not shown) installed in a supply unit 201 for removing dust particles or the like, is allowed to flow in an SUS pipe 202 provided for a head cover 203, and supplied from the ink jet recording head side into the ink flow paths which are formed by adhesively bonding the heater board 204 and the ceiling plate 205. Then, the discharge energy generating elements provided for the heater board 204 supply discharge energy to ink in accordance with electric signals from the PWB 208 which is a printed base board for exchanging electric signals with a recording apparatus (not shown). In other words, when the discharge energy generating elements are electrothermal converting devices, ink is heated to be bubbled, and ink is discharged by means of pressure exerted by this bubbling.
In this way, recording is made by discharging ink to a recording medium. However, when the ink jet recording head operates continuously, the temperature of the head itself is caused to rise, and may produce unfavorable effect on recording in some cases. To counteract this, the base plate 106 is provided with heat radiating function, and it is formed by metallic material, such as aluminum alloy die-casting material, which has excellent mechanical property, machinability, and forgeability in addition to good thermal conductivity. Also, the surface of the base plate 106 is treated with anodized aluminum to provide erosion resistivity to prevent it from being eroded by ink.
Also, the recording apparatus having an ink jet recording head mounted thereon performs the recovery operation to remove ink adhering to the discharge surface by use of a blade to brash off the discharge surface on which discharge ports are formed to discharge ink from the ink jet recording head, thus stabilizing the discharge characteristics.
However, the elongated conventional ink jet recording head is structured so that the spring unit is added to hold down the ceiling plate and heater board with each other, besides the supply path for supplying ink, which is arranged above the ceiling plate. As a result, the number of components is increased, and the step of manufacturing processes is also increased eventually.
Also, in some cases, the countermeasures have not been taken sufficiently as to the straightness in the longitudinal direction, the prevention of thermal distortion that may take place on the structural members due to the temperature rise characteristic of an elongated head, as well as the deformation of head caused by the linear expansion difference of materials affected by the changes of environmental temperature. For example, the metallic material, such as aluminum, used for the base plate has a large thermal expansion coefficient, and is subjected to easier deformation by temperature changes. As a result, warping may occur in the mode of head in some cases.
Now, therefore, it is considered useful to select a material having a smaller thermal expansion coefficient, such as isotropic graphite, for the base plate material used for a printing head of as high as 600 dpi. The isotropic graphite has dually such characteristics as being strong against heat and chemicals, besides light in weight.
Nevertheless, the isotropic graphite has intergranular or inner texture defects or contains in it pores and microscopic cracks. As a result, the isotropic graphite has a high water absorption, and absorbs ink adhering to it eventually. Thus, on the surface of blading plane of the isotropic graphite which is brushed off by a blade, a considerable amount of ink is absorbed, and if the amount of ink thus absorbed reaches the critical state, ink is exuded, on the contrary, from the surface of the blading plane to wet it. Then, if the amount of ink which is brushed off exceeds the allowable amount after repeated recovery, ink cannot be brushed off completely, hence creating a problem that the recovery operation cannot be executed sufficiently.
Also, the intergranular binding power of isotropic graphite is small to make it easier to create carbon particles on the surface thereof, and processed plane as well, which of course brings about the creation of dust particles, and also, causes cut-offs or cracks when handling it for assembling or installation. Further, for that matter, a threaded female hole is subjected to being broken if screwed with an intensified value of torque, which necessitates a margin up for the strength of thread cutting.
Furthermore, beside the problems discussed above, the bubbles which are created in the ink supply path are stagnated at the filter portion or the ink supply or recovery efficiency of pressurized ink is reduced eventually.
It is an object of the present invention to provide an ink jet recording head for which the straightness is secured in the longitudinal direction without increasing the number of components, and a method for manufacturing such ink jet recording head.
It is another object of the invention to provide an ink jet recording head which does not impede the recovery operation thereof, and a method for manufacturing such ink jet recording head.
The ink jet recording head of the present invention comprises a substrate having the element surface provided with energy generating elements for generating energy to be used for discharging ink; a ceiling plate provided with the grooved surface having grooves to become ink passage corresponding to the energy generating elements, the grooved surface and the element surface being bonded to form the ink passage; a base plate for supporting the substrate from the side opposite to the element surface; and an ink supply member being in contact with the base plate at a contact portion, having the ink flow path wall face to be communicated with the ink passage. For this recording head, the base plate and the ink supply member pinch the substrate and the ceiling plate at the contact portion as a fulcrum so as to enable the base plate to press the substrate from the side opposite to the element surface, and the ink supply member to press the ceiling plate from the side opposite from the grooved surface.
For the ink jet recording head of the invention thus structure, the member that enables the ceiling plate and the substrate to be closely in contact, and the member for supplying ink are arranged to be commonly functional as an ink supply member. As a result, it becomes possible to omit the provision of any spring member to be used only for keeping the close contact of the ceiling plate and the substrate, thus curtailing the number of parts.
Also, for the ink jet recording head of the present invention, it may be possible to fix the ink supply member and the base plate member by use of screws to enable them to be in close contact with each other at the contact portion or to fix the ink supply member and the base plate member by adhesively bonding them with each other at the contact portion. In the case of adhesive bonding, in particular, it is possible to omit screws for fixing use.
Also, the ink jet recording head of the present invention may be the one in which the printed base plate for controlling the energy generating elements is installed on the base plate on the side that supports the substrate so as not to intervene in the contact between the ink supply member and the base plate, and the surface of the base plate for installing the printed base plate may be formed at a position lower than the surface for supporting the substrate. With the structure thus arranged, it becomes possible to preferably effectuate wire bonding by making the height of wire bonding substantially the same between the printed base plate and the substrate particularly when wire bonding is adopted to electrically connect the substrate and the printed base plate which is thicker than the substrate.
Also, the ink jet recording head of the invention may be the one which further comprises an ink supply second member having an ink supply path communicated with the ink flow path by being bonded to the ink supply member. The ink supply second member and the base plate may be in close contact and fixed by use of screws or my be bonded with each other and fixed.
Also, a filter may be installed in the ink supply path to make the ink flow-in direction substantially upward vertically. The filter may be provided in a plurality, and of the plural filters, the ink passing area of the filter installed in the ink supply path for supplying ink from the outside to the ink passage is larger than the ink passing area of the filter installed in the ink supply path for returning ink from the ink passage to the outside. In this case, it becomes possible for the bubbles that flow together with ink to utilize floating force and pass each of the filters easily, thus preventing the ink flow from being blocked by the stagnation of bubbles on the flow-in side of each of the filters. Also, with the passing area of ink of the filter on the return side being made smaller in agreement with the reduced pressure of flowing ink, it becomes possible to apply pressure to the bubbles in the filter on the return side to enable them to pass through the filter. In this manner, the designing elements required for the recovery system on the recording apparatus side can be reduced accordingly.
Also, the contact portion of the ink supply members themselves may be sealed with an O-ring or with sealant.
Further, the ink passage may be airtightly closed essentially with the exception of the communication port of the ink flow path and discharge port for discharging ink. In this case, ink in the ink passage is not allowed to be in contact with external sealant or the like.
Also, the contact portion of the ink flow path and the communication port may be sealed with an O-ring or with sealant.
Also, above the energy generating element, a valve may be integrally formed with the substrate, and the free end of this valve is in the direction toward the discharge port for discharging ink and the fixing end in the direction opposite to that direction.
Also, for the ink jet recording head of the invention, the energy generating element is an electrothermal converting device for generating thermal energy. The ink supply member and the base plate are formed by the same material, and the substrate and the ceiling plate are formed by the same material. Then, the difference between the linear expansion coefficients of the ink supply member and the base plate, and the linear expansion coefficients of the substrate and the ceiling plate may be arranged so as not to allow intervention in the valve and the wall face of the ink passage even if a pitch deviation is created by the heat generated by the electrothermal converting device in the arrangement direction of the discharge port for discharging ink. In this case, even if a pitch deviation is created between the substrate and the ceiling plate by being pulled by the linear expansion of the base plate, for example, the valve and the ink passage wall face do not intervene with each other, hence making it possible to prevent the discharge characteristics from being deteriorated. Also, the ink supply member and the base plate are formed by the same material, and the substrate and the ceiling plate are formed by the same material. Then, the difference between the linear expansion coefficients of the ink supply member and the base plate, and the linear expansion coefficients of the substrate and the ceiling plate may be made smaller than the difference between the linear expansion coefficient of metal and the linear expansion coefficients of the substrate and the ceiling plate.
The ink supply member may be provided with thermal conductivity capable of preventing harmful effects due to thermal shocks from the electrothermal converting device, and the base plate may be provided with thermal conductivity capable of preventing harmful effects due to thermal shocks from the electrothermal converting device. In this case, it becomes possible to prevent each member from the compositional deformation or distortion due to thermal shock that may be given to each structural member when the temperature of the entire body of the ink jet recording head is caused to rise in operating a solid recording or the like.
Also, the ink supply member and the base plate may be formed by carbon graphite. Then, this formation is anticipated to contribute to making the ink jet head lighter in weight, besides obtaining the thermal characteristics described earlier.
Also, for the ink jet recording head of the invention, the face of the ink supply member and that of the base plate which form the surface having discharge ports for discharging ink may be provided with water repellency. In this case, it becomes possible to prevent the defective recovery operation due to the ink permeation into the surface where discharge ports are formed.
A protection layer may be formed substantially on the entire outer surfaces of the ink supply member and the base plate in order to block ink impregnation.
Also, the inner defects, pores, and microscopic cracks of the ink supply member and the base plate may be impregnated with liquid agent that permeates them. In this case, with the liquid agent being hardened, the binding force between particles is intensified to provide the function of increasing the margin of the preventions of chipping, carbon dust particles, breakage of threads on the tapped portions.
The method of the present invention for manufacturing an ink jet recording head, which is provided with a substrate having the element surface with energy generating elements formed thereon for generating energy to be used for discharging ink; a ceiling plate having the grooved surface with grooves to become ink passage corresponding to the energy generating elements, the grooved surface and the element surface being bonded to form the ink passage; a base plate for supporting the substrate from the side opposite to the element surface; and an ink supply member being in contact with the base plate at a contact portion, having the ink flow path wall face to be communicated with the ink passage, comprises the steps of preparing an ink supply member having the ink flow path wall face to be communicated with the ink passage; bonding the ink supply member and the base plate; and pinching the substrate and the ceiling plate with the base plate and the ink supply member for contacting them closely by pressing the substrate with the base plate from the side opposite to the element surface, and pressing the ceiling plate with the ink supply member from the side opposite to the grooved surface.
With the method for manufacturing an ink jet recording head of the invention thus structured, it is possible to prepare the member for supplying ink and the member for enabling the ceiling plate and the substrate to be closely in contact to be commonly functional as the ink supply member. Therefore, not only a step of installing the spring member which is used only for maintaining the ceiling plate and the substrate to be in close contact can be omitted, but also, the cost reduction, the simplification of the apparatus, and the processing yield can be enhanced.
This method for manufacturing an ink jet recording may comprise further the step of preparing a ink supply second member having the ink supply path communicated with the ink flow path by being bonded to the ink supply member. Also this method may further comprise the step of forming a protection layer for blocking the ink permeation substantially on the entire outer surface of the ink supply member and the base plate. Further, the method may comprise the step of coating with water repellent agent the face of the ink supply member and the face of the base plate to form the surface provided with discharge ports for discharging ink after the completion of the step of forming the protection layer.